Optimise TransactionPool.addRemoteTransaction (#1448)

* Bail out of addRemoteTransactions immediately if we're not in sync instead of after we sort by nonce and begin iterating.

* Don't sort transactions by nonce. This was only required because we previously rejected transactions where the nonce was too high.

ethereum/eth/src/main/java/tech/pegasys/pantheon/ethereum/eth/transactions/TransactionPool.java

@@ -33,9 +33,7 @@
 import tech.pegasys.pantheon.ethereum.mainnet.TransactionValidator.TransactionInvalidReason;
 import tech.pegasys.pantheon.ethereum.mainnet.ValidationResult;
 
-import java.util.ArrayList;
 import java.util.Collection;
-import java.util.Comparator;
 import java.util.HashSet;
 import java.util.List;
 import java.util.Optional;
@@ -106,11 +104,11 @@ public ValidationResult<TransactionInvalidReason> addLocalTransaction(
   }
 
   public void addRemoteTransactions(final Collection<Transaction> transactions) {
+    if (!syncState.isInSync(SYNC_TOLERANCE)) {
+      return;
+    }
     final Set<Transaction> addedTransactions = new HashSet<>();
-    for (final Transaction transaction : sortByNonce(transactions)) {
-      if (!syncState.isInSync(SYNC_TOLERANCE)) {
-        return;
-      }
+    for (final Transaction transaction : transactions) {
       final ValidationResult<TransactionInvalidReason> validationResult =
           validateTransaction(transaction);
       if (validationResult.isValid()) {
@@ -130,13 +128,6 @@ public void addRemoteTransactions(final Collection<Transaction> transactions) {
     }
   }
 
-  // Sort transactions by nonce to ensure we import sequences of transactions correctly
-  private List<Transaction> sortByNonce(final Collection<Transaction> transactions) {
-    final List<Transaction> sortedTransactions = new ArrayList<>(transactions);
-    sortedTransactions.sort(Comparator.comparing(Transaction::getNonce));
-    return sortedTransactions;
-  }
-
   public void addTransactionListener(final PendingTransactionListener listener) {
     pendingTransactions.addTransactionListener(listener);
   }